Validation of the Nox-T3 Portable Monitor for Diagnosis of Obstructive Sleep Apnea in Patients With Chronic Obstructive Pulmonary Disease

Study Objectives: Clinical practice guidelines recommend polysomnography (PSG) for diagnosis of obstructive sleep apnea (OSA) in patients with major comorbidities. We evaluated home sleep apnea testing (HSAT) using a type 3 portable monitor (PM, Nox-T3, Nox Medical, Reykjavik, Iceland) to diagnose OSA in adults with chronic obstructive pulmonary disease (COPD). Methods: Ninety adults with COPD (89.0% males, mean +/- standard deviation age 66.5 +/- 7.8 years, body mass index 27.5 +/- 5.8 kg/m(2), forced expiratory volume in the first second/forced vital capacity [FEV1/FVC] 53.5 +/- 12.4%, FEV1 54.0 +/- 18.4% predicted) underwent unattended HSAT followed by an in-laboratory PSG with simultaneous PM recording. Results: Scoring hypopneas with a >= 4% oxygen desaturation, the apnea-hypopnea index (AHI) was 16.7 +/- 20.6 events/h on HSAT, 20.0 +/- 23.3 events/h on in-laboratory PM, and 21.2 +/- 26.2 events/h on PSG (P <.0001). Bland-Altman analysis of AHI on HSAT versus PSG showed a mean difference (95% confidence interval) of -5.08 (-7.73, -2.42) events/h (P =.0003) and limits of agreement (+/- 2 standard deviations) of -30.00 to 19.85 events/h; HSAT underestimated AHI to a greater extent for more severe values (rho = -. 529, P <.0001). Using an AHI = 5 events/h to diagnose OSA, HSAT had 95% sensitivity, 78% specificity, 88% positive predictive value, and 89% negative predictive value compared to PSG. Mean oxygen saturation was 93.2 +/- 3.7% on PSG, 91.0 +/- 3.3% on in-laboratory PM, and 90.8 +/- 4.0% on HSAT (P <.0001). Percentage time oxygen saturation = 88% was 17.9 +/- 26.4% on HSAT, 17.4 +/- 25.5% on in-laboratory PM, and 10.0 +/- 21.1% on PSG (P <.0001). Conclusions: The Nox-T3 PM can be used to diagnose OSA in patients with COPD but, most likely due to differences among pulse oximeters, a greater number of patients with COPD and without OSA qualified for nocturnal oxygen treatment using this PM than PSG.